Shape Control of Ca₂Nb₃O₁₀ Nanosheets: Paving the Way for Monolithic Integration of Functional Oxides with CMOS

Abstract

In order to integrate functional oxides with Complementary Metal Oxide Semiconductor (CMOS) materials, templates to ensure their epitaxial growth are needed. Although oxide nanosheets can be used to direct the thin film growth of transition metal oxides in a single out-of-plane orientation, the in-plane orientation of individual nanosheets within a nanosheet-based film is totally random. Here, we show the ability to improve the in-plane orientation of Ca₂Nb₃O₁₀ nanosheets, and hence of SrRuO₃ films grown on them by controlling their external shape. The parent-layered perovskite KCa₂Nb3O₁₀ particles were formed in square-like platelets, thanks to the anisotropic growth in molten K₂SO₄ salt, as opposed to the formation of irregular platelets in a solid-state reaction. The exfoliation of HCa₂Nb₃O₁₀, which is the protonated form of KCa₂Nb₃O₁₀, was optimized to retain the square-like shape of Ca₂Nb₃O₁₀ nanosheets. Electron backscatter diffraction confirmed the improved in-plane orientation among square-like Ca₂Nb₃O₁₀ nanosheets with the formation of larger SrRuO₃ domains. As a result, SrRuO₃ films showed the lower resistivity and higher residual resistivity ratio, ρ_300K/ρ_2K, on square-like Ca₂Nb₃O₁₀ nanosheets than on irregularly shaped nanosheets of similar lateral nanosheet size.

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